Let us return for a moment to the assertion from Lévy-Leboyer that during the course of their industrialization the French and British economies ‘simply made maximum use of the factors of production available – in the one case labour, in the other capital’ [68, 292]. This implies that if the labour supply was a source of strength in France, capital was something of a weakness. There was indeed a time when the early start made by the British on the path of industrialization was attributed to an abundance of capital. Economic theory appeared to justify this interpretation, with models in which the rate of growth of output was determined by the level of investment. A common assertion was that a vital difference between ‘preindustrial’ and industrial economies was that the former saved and invested 4 or 5 per cent of national income, the latter a minimum of 12 to 15 per cent. But in the French case, econometricians have noted a disconcerting decline in the investment ratio during the late nineteenth century. A recent estimate shows the share of national product invested at home falling from 12.0 per cent in 1850–59 to 11.7 per cent in 1879 – and doing much the same again between the 1880s and the 1890s [79, 239], A promising explanation for French ‘stagnation’ looms on the horizon … However, another school of thought in economics countered by playing down the role of capital formation in economic growth, emphasizing instead the overwhelming impact of technical progress.